Reaction condition: 1.0 wt. % lignin, 10 g microemulsion (WW :WO :WP = 15.7 :9.2 :75.1, wt. %), 0.1 mmol catalyst, 1 MPa O2, 413 K, 4 h. Note: HB-p - hydroxybenzaldehyde; PHB- propyl-4-hydroxybenzoate.